thank's for answering me, i was trying and the big trouble is that there is
a css stylesheet that contains al de colors for the rows, alternate rows,
and special cells, and some cells are re-styled in the gridview_rowdatabound
event so i must use this styles and i must convert the gridview, not the
dataset... mi big trouble now is the fact that the color are in css
classes...and i don't know hot to access this information...

if i can do some like
me.getcssclass(me.gridview1.rows(0).cells(0).cssclass).backgroundcolor  then
i have my problem solved!, but i can't find information about how to get the
specification of some class included in an attached file to an aspx with the
<link href="Styles/Normal.css" rel="stylesheet" type="text/css" />
directive.

there is the code i'm using... and i don't understand why the colors are not
rendered ... i supose that is because is the browser itself who paints the
colors in te last step:

public sub Excel()
Dim sb As StringBuilder = New StringBuilder()
Dim sw As StringWriter = New StringWriter(sb)
Dim hw As HtmlTextWriter = New HtmlTextWriter(sw)
Dim pag As Page = New Page()
Dim frm As HtmlForm = New HtmlForm()
Dim gv As GridView = Me.GVResultado

pag.EnableEventValidation = False
gv.AllowPaging = False
gv.EnableViewState = False
gv.DataBind()
If (Not (gv.HeaderRow) Is Nothing) Then
PrepareControlForExport(gv.HeaderRow)
End If
For Each row As GridViewRow In gv.Rows
PrepareControlForExport(row)
Next
If (Not (gv.FooterRow) Is Nothing) Then
PrepareControlForExport(gv.FooterRow)
End If

pag.DesignerInitialize()
pag.Controls.Add(frm)
frm.Controls.Add(gv)
pag.RenderControl(hw)
Response.Clear()
Response.Buffer = True
Response.ContentType = "application/vnd.ms-excel"
Response.AddHeader("Content-Disposition", "attachment;filename=data.xls")
Response.Charset = "UTF-8"
Response.ContentEncoding = Encoding.Default
Response.Write(sb.ToString())
gv.AllowPaging = True
gv.EnableViewState = True
gv.DataBind()
Response.End()
end sub